Process for producing polypropylene foam

摘要

The invention relates to the process of the invention provides a radiation-crosslinked polypropylene foam by extrusion at a low temperature (about 170 DEG C.) below the decomposition point of the blowing agent. The resulting foamed item has by far better heat resistance than conventional ones. The raw resin can be prepared by mixing a resin in the pellet form and a blowing agent in the powder form on account of the low-temperature flowability. Heretofore, such mixing was impossible because the blowing agent does not disperse completely. This outstanding effect of the invention was not expected at all from the known prior arts.